Urface sterilization

ABSTRACT

A surface sterilization method and blowtorch or burner for used in connection therewith. Jets of an ignited combustible mixture and a sterilizing fluid are projected toward a surface to be sterilized. The sterilizing fluid is heated by the flame of the burner and then contacts the surface to be sterilized in order to achieve sterilization. In a preferred form, saturated steam is used as the sterilizing fluid. The saturated steam becomes superheated as it expands when it leaves the burner and as it is heated by the flame thereof. The amount of saturated steam which leaves the burner is controlled to effect at least partial condensation of the superheated steam on the surface to be sterilized and the condensate is then re-evaporated with the aid of the heat of the flame. The blowtorch or burner construction establishes jets of an ignited combustible mixture and the sterilizing fluid which are mixed exteriorly of the burner.

Beauvais et al.

[ Sept. 17, 1974 SURFACE STERILIZATION Inventors: Max P. lBeauvais,Eure; Jacques Breil, Paris, both of France [73] Assignee: ReynoldsMetals Company,

Richmond, Va.

Filed: July 26, 1972 Appl. No.: 275,430

[5 6] References Cited UNITED STATES PATENTS 7/1934 Mexis 431/190 6/1936Lechler 21/118 UX 6/1941 Morris 21/2 11/1959 Nieman et a1. 239/5498/1965 James 239/549 X Primary Examiner-Joseph Scovronek AssistantExaminer-Amold Turk Attorney, Agent, or Firm--Glenn, Palmer, Lyne &Gibbs [57] ABSTRACT A surface sterilization method and blowtorch orburner for used in connection therewith. Jets of an ignited combustiblemixture and a sterilizing fluid are projected toward a surface to besterilized. The sterilizing fluidis heated by the flame of the burnerand then contacts the surface to be sterilized in order to achievesterilization. In a preferred form, saturated steam is used as thesterilizing fluid. The saturated steam becomes superheated as it expandswhen it leaves the burner and as it is heated by the flame thereof. Theamount of saturated steam which leaves the burner is controlled toeffect at least partial condensation of the superheated steam on thesurface to be sterilized and the condensate is then re-evaporated withthe aid of the heat of the flame. The blowtorch or burner constructionestablishes jets of an ignited combustible mixture and the sterilizingfluid which are mixed exteriorly of the burner.

3 Claims, 4 Drawing Figures PAIENIEUSEH 71914 Fig.3.

SURFACE STERIILIZATION This invention relates to a method of surfacesterilization and a burner construction for use therewith and, moreparticularly, to such a method which utilizes a sterilizing fluid whichis heated by the flame of the burner.

It has been known heretofore to use a burner or blowtorch flame in orderto effect surface sterilization solely by the burner flame. In suchdevices, the flame must be capable of raising the surface temperaturesufficiently high in order to achieve sterilization. The nature of thesurface constitutes a limiting factor on the use of flame heating andmany surfaces are damaged or destroyed if the temperature exceeds agiven threshold level for the particular surface.

It is also known that, for a given temperature, a greater sterilizingaction takes place if the ambient or environmental conditions in whichthe surface is lo cated contains a substantial amount of water or watervapor as contrasted with relatively dry ambient air with low relativehumidity.

The present invention overcomes the disadvantages of previously knownflame treatment devices by modifying the jet discharge of a blowtorch orburner to include a sterilizing fluid inaddition to the flame itself. Ina preferred form of the invention, saturated steam is introduced intothe burner. The saturated steam becomes superheated as it is expandedand heated upon being discharged from the burner.

A further difficulty is experienced in using saturated steam becauseafter it becomes superheated it also tends to condense in theenvironment of relatively cool room temperature and the temperature ofthe surface to be sterilized. As is well known, this condensation maycause or provoke a regrouping of bacteria on the surface and result incertain contaminated zones or pockets.

In accordance with the present invention, this further difficulty isobviated in a preferred form of the invention by controlling the amountof steam admitted vis-avis the amount of combustible gases burned toensure that the condensate is re-evaporated under the influence of asufficient temperature.

Accordingly, it becomes possible in a preferred form of the invention toproject simultaneously toward the surface to be sterilized jets of anignited combustible mixture and a sterilizing fluid. The sterilizingfluid is heated by diffusion with the ignited combustible mixture orflame of the burner and it contacts the surface to be sterilized inorder to effect sterilization. Furthermore, it has been found that byprojecting simultaneously toward the surface to be sterilized jets of anignited combustible mixture and a sterilizing fluid at a temperaturesufficient to sterilize the surface without destroying it and byeffecting condensation and reevaporation that maximum sterilizationoccurs at a minimum temperature.

The inherent advantages and improvements of the present invention willbecome more readily apparent upon considering the following detaileddescription of the invention and by reference to the drawings in which:

FIG. I is a fragmentary plan view of the underside of a burnerconstruction illustrating one embodiment of the present invention;

FIG. 2 is an elevational view taken in vertical cross sectionsubstantially along a major axis of the burner shown in FIG. I;

FIG. 3 is a fragmentary plan view of the underside of a burnerconstruction illustrating another embodiment of the present invention;and,

FIG. 4 is an elevational view taken in vertical cross sectionsubstantially along a major axis of the burner shown in FIG. 3.

Referring now to FIGS. 1 and 2, a blowtorch or burner construction isillustrated to have an input I for a mixture of combustible gases. Input1 is shown in the form of a pipe welded to the side of the burner and itcommunicates directly with a toroidal mixing chamber 2. A plurality ofcircularly arranged nozzles 3 extend outwardly from the mixing chamber 2to the tip of the burner. Jets of flame issue directly out from nozzles3 when the combustible gases, such as propane and oxygen, are ignited.

The blowtorch or burner is also illustrated to have an input 4 for asterilizing fluid which is illustrated to consist of a pipe welded tothe burner. Input 4 communicates with central diffuser means 5 wherebythe sterilizing fluid is separated into a plurality of discrete jets.These jets are substantially parallel to the output of nozzles 3 which,as illustrated best in FIG. ll, are arranged around the outer peripheryof the jets of sterilizing fluid. If desired, the arrangement could bereversed with the combustible mixture entering at the center and thejets of sterilizing fluid entering peripherally in a ring.

The apparatus is provided with suitable valve controls, not shown, forthe inputs of both the combustible gases and the sterilizing fluid.These controls, which are standard for blowtorches or burners, make itpossible to adjust the ratio of combustible gas mixture with respect tothe sterilizing fluid which is: introduced into the burner.

In a preferred form of the invention, saturated steam is used as thesterilizing fluid and any suitable combustible mixture, such as propaneand oxygen, may be used. The saturated steam becomes superheated as itexpands upon leaving the burner in discrete jets and is heated by theflame from the burner. Because the ambient air and surface to besterilized, such as the inside surface of a container body, are at asubstantially lower temperature, such as room temperature, condensationof the superheated steam occurs on the container body. By controllingthe amount of steam projected in the heated jets, the condensate isre-evaporated, thereby avoiding the danger ofa build-up of bacteria inthe condensate. This method thus takes advantage of the heat ofvaporization of the sterilizing fluid and results in maximumsterilization at a minimum temperature. This, of course, ensures thatthe process may be practiced on a large number of surfaces withoutdestroying them.

Referring now to FIGS. 3 and 4, another embodiment of the blowtorch orburner is disclosed and wherein the same reference numerals are used todesignate the same component parts. In this embodiment, the input Iagain communicates with a toroidal mixing chamber 2. However, in thisembodiment the face of the burner is substantially square so as toconform to the outline of a substantially square surface to be treated.The jets from nozzles 3 alternate with the jets from the diffuser means5 which again separate the sterilizing fluid introduced at 4 into aplurality of discrete jets. In this form of the invention, the diffusermeans 5 constitute a plurality of radially extending passageways (asviewed in FIG. 3) each of which communicates with the sterilizing fluidinput 4. The alternating nozzle arrangement is also shown to besubstantially radial in FIG. 3 but the passageways thereto communicatewith the toroidal mixing chamber 2.

In an actual reduction to practice, saturated steam at a temperaturemaintained between 300F. and 350F. and having a boiler pressure ofapproximately 150 psi (pounds per square inch) was introduced into input4 where it still had a pressure of from approximately 100-140 psi.Oxygen and propane constituted the combustible gas mixture and thesegases were introduced at input 1 of a burner arrangement as shown inFIGS. 1 and 2. The oxygen was taken from a source at psi and the propanewas taken from a source at 10 psi. The quantity of steam was controlledthrough a valve so that a small but perceptible amount of condensationoccurred on the surface to be sterilized which consisted of an open-topcup-shaped container. The diameter of the burner was approximately 1%inches. The amount of steam was varied until all condensate wasreevaporated on the surface of the container to be sterilized. At adistance of about 8 inches from the face of the burner, the temperaturewas measured to be approximately 800F.

Other combustible gases, including natural gas, can be used as thecombustible gases and other fluids, liquids or gases, can be used inplace of steam. Also, the distribution or arrangement ofjets of flamesand sterilizing fluids may vary depending upon the surface to betreated. A plurality of burners may be used in series. Also, it ispossible to use a large number of burners with small cross sections anda small number of sterilizing fluid diffusers of large diameter, or,conversely, large burners and many small diffusers.

While presently preferred embodiments of the invention have beenillustrated and described, it will be recognized that the invention maybe otherwise variously embodied and practiced within the scope of theclaims which follow.

What is claimed is:

l. A method of sterilizing the surface of a container body utilizing aflame of a burner comprising the steps of (a) projecting jets of anignited combustible mixture and jets of a sterilizing fluid from nozzlesformed in a burner diffuser, (b) heating said sterilizing fluid withsaid ignited combustible mixture by mixing said jets externally of saidburner diffuser, (c) and establishing contact between sterilizing fluidand said surface for a length of time sufficient to sterilize saidsurface without destroying said surface.

2. A method of sterilizing a surface as claimed in claim ll, whereinsaid sterilizing fluid comprises steam and said method includes thesteps of super-heating said steam at the outlets of said burnerdiffuser.

3. A method of sterilizing a surface as claimed in claim 2, includingthe additional steps of controlling by means of a valve setting theamount of steam projected to effect at least partial condensation ofsaid superheated steam on said surface to be sterilized andreevaporating said condensate with the aid of heat from said ignitedcombustible mixture.

i =l= a

2. A method of sterilizing a surface as claimed in claim 1, wherein saidsterilizing fluid comprises steam and said method includes the steps ofsuper-heating said steam at the outlets of said burner diffuser.
 3. Amethod of sterilizing a surface as claimed in claim 2, including theadditional steps of controlling by means of a valve setting the amountof steam projected to effect at least partial condensation of saidsuperheated steam on said surface to be sterilized and re-evaporatingsaid condensate with the aid of heat from said ignited combustiblemixture.